1. Field of the Invention
The present invention relates to a lens assembly having a movable lens. More particularly, the present invention relates to a lens assembly having a movable lens in which heat generated harmfully from an electronic device can be eliminated to keep the inside cooled effectively.
2. Description Related to the Prior Art
A digital still camera is widely used, in which an image pickup device such as a CCD image sensor is used to photograph an image to produce image data of a digital form. The image data is written to a storage medium such as a built-in data storage, memory card and the like. Examples of the digital still camera include a lens exchangeable type in which a selected one of plural lens assemblies is set and used for the purpose of photography. A camera main unit is combined with a lens assembly to constitute the digital still camera of a lens exchangeable type. In general, the image pickup device is incorporated in the camera main unit. It is necessary optically to connect lens groups in the lens assembly to the image pickup device of the camera main unit in mounting the lens assembly. This makes it difficult for unskilled users to handle the digital still camera because of necessity of back focus adjustment and other conditions.
Types of the digital still camera in which the image pickup device is incorporated in the lens assembly are known with the purpose facilitating handling of the digital still camera of the lens exchangeable type. There is no need of optical connection of the lens assembly. Electric connection of the lens assembly with the camera main unit is easy for users to handle. There is a further advantage in the image pickup device built-in type of the lens assembly in that a chamber for the image pickup device can be tightly closed, to protect the inside with the image pickup device from entry of dust, dirt or other foreign material. However, the image pickup device built-in type of the lens assembly has a shortcoming in smaller efficiency in cooling because of a small space in the lens assembly for containing the image pickup device and circuits for driving the image pickup device. Performance of various circuits may be lower due to the smaller efficiency of cooling.
Various techniques have been suggested for cooling parts generating heat in an apparatus. JP-A 8-167751 discloses a laser apparatus in which a solid state laser device is excited by use of semiconductor laser light. Heat dissipating fins are secured to the apparatus. JP-A 2002-112082 discloses the digital still camera in which the lens assembly protrudes. Parts which will generate heat are disposed on a lateral side of the lens assembly. Heat dissipating fins are secured to those parts. JP-A 5-034605 discloses the digital still camera removably connected with an endoscope. A fan mechanism is disposed on a rear of the image pickup device which will generate heat.
However, JP-A 8-167751 and 2002-112082 disclose only the use of the heat dissipating fins, panels or the like. Efficiency of cooling cannot be higher than is intended by the fins, because of lack of further control. JP-A 5-034605 has a shortcoming in that the fan mechanism for cooling requires a sufficient space in the digital camera. The size of the digital camera and the number of the parts for this become greater, to raise the manufacturing cost.